Alignment issue.
 

Wanna find out what the problem might be.

When i got my aftermarket rims i got an alignment cause the car was pulling to the right slightly. I found out later that one of my ball joints was on the verge of snapping (found out right after a 600k road trip :(). My mechanic said the other one seemed fine and he showed me the differnce. But now the car is pulling to the right again and has been for a couple months. Would this be because of the ball joint or what might the problem be? Im gonna get another alignment as soon as i put my summer rims back on so i wanna try to know ahead of time what the issue might be so i can take it to my mech.